Isada N B, Qureshi F, Jacques S M, Holzgreve W, Tout M J, Johnson M P, Evans M I
Department of Obstetrics and Gynecology, Hutzel Hospital/Wayne State University, Detroit, Mich. 48201.
Fetal Diagn Ther. 1993 Nov-Dec;8(6):423-8. doi: 10.1159/000263862.
Meroanencephaly is a rare form of anencephaly characterized by malformed cranial bones and a median cranial defect, through which protrudes abnormal tissue, called the area cerebrovasculosa. Area cerebrovasculosa denotes abnormal spongy, vascular tissue admixed with glial tissue ranging from a thin membrane to a large pseudoencephalic mass simulating cerebral tissue, that is composed of connective tissue, hemorrhagic vascular channels, glial nodules, and disorganized choroid plexuses. There are three types of anencephaly: (1) meroanencephaly, where there is rudimentary brain tissue and partial formation of the cranium; (2) holoanencephaly, the most common type, in which the brain is completely absent, and (3) craniorachischisis, the most severe, where area cerebrovasculosa and area medullovasculosa fill both cranial defects and the spinal column. In meroanencephaly, there is a median defect present, through which protrudes the area cerebrovasculosa. We present 3 cases of meroanencephaly diagnosed prenatally, along with histopathologic analysis. One case showed ectopic glial tissue in the lung and adrenal medullary hyperplasia. Two cases were diagnosed in the early second trimester by ultrasound scanning. Meroanencephaly may be mistaken for encephalocele both at the bedside exam and sonographically, and should be included in the differential for protruding anterior cranial masses.
半叶无脑畸形是无脑畸形的一种罕见形式，其特征为颅骨畸形和颅骨正中缺损，通过该缺损突出异常组织，称为脑血管区。脑血管区指异常的海绵状血管组织，混有神经胶质组织，范围从薄膜到模拟脑组织的大型假性脑块，由结缔组织、出血性血管通道、神经胶质结节和杂乱的脉络丛组成。无脑畸形有三种类型：（1）半叶无脑畸形，存在残留脑组织和部分颅骨形成；（2）全无脑畸形，最常见的类型，其中大脑完全缺失；（3）颅脊柱裂，最严重的类型，脑血管区和脊髓血管区充满颅骨缺损和脊柱。在半叶无脑畸形中，存在正中缺损，脑血管区通过该缺损突出。我们报告3例产前诊断的半叶无脑畸形病例，并进行组织病理学分析。1例显示肺内异位神经胶质组织和肾上腺髓质增生。2例在孕中期早期通过超声扫描诊断。半叶无脑畸形在床边检查和超声检查中都可能被误诊为脑膨出，在鉴别前颅突出肿块时应考虑到这种情况。
